I had a person re-grout the 4 tiles years ago. That person was a dufus and left some grout on the tiles instead of just in the grooves.. It is still there! How could I remove the small patches of grout from the front of the white tiles? As a point of information, the repair guy messed up by grouting ALL of the tiles when he first started. The grout drys so fast that it set up hard before it could be struck and finished and the excess washed off. The tile setter guy is supposed to do just a very few tiles at a time.
Hopefully, all of your tiles have grout AND sealer. You can try plain ol' scrapping it off, but be careful not to scratch the tiles. Try using white vinegar to soften the grout, but be sure not to get any on the grout that you want to save. Use a small sponge, or even Q-tips. You may have to let it soak a few minutes. Also, try using a plastic scraper instead of a metal one, like a pan scraper. If you have any spare tiles, practice scraping to see if you're scratching the tile.
